import java.util.HashMap;
import java.util.Objects;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: mac
 * Date: 2022-10-27
 * Time: 20:07
 */
class Person {
    public String ID;

    public Person(String ID) {
        this.ID = ID;
    }

    //equals跟hashcode为什么必须一起重写

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Person person = (Person) o;
        return Objects.equals(ID, person.ID);
    }

    @Override
    public int hashCode() {
        return Objects.hash(ID);
    }

    @Override
    public String toString() {
        return "Person{" +
                "ID='" + ID + '\'' +
                '}';
    }
}
public class HashBuck2 <K,V>{

    static class Node<K,V> {
        public K key;
        public V val;
        public Node<K,V> next;

        public Node(K key, V val){
            this.val = val;
            this.key = key;
        }
    }

    public Node<K,V>[] array = (Node<K,V>[])new Node[10];
    public int usedSize;
    public static final double DEFAULT_LOADFACTOR = 0.75;


    public void put(K key,V val){
        int hash = key.hashCode();
        int index = hash % array.length;
        Node<K,V> cur = array[index];
        while (cur != null){
            if (cur.key.equals(key)){
                cur.val = val;//更新val值
                return;
            }
            cur = cur.next;
        }
        Node<K,V> node = new Node<>(key, val);
        node.next = array[index];
        array[index] = node;
        this.usedSize++;

        if (loadFactor() > DEFAULT_LOADFACTOR){
            resize();//重新hash
        }
    }
    private void resize() {
        Node<K,V>[] newArray = new Node<>[array.length * 2];
        for (int i = 0; i < array.length; i++) {
            Node<K,V> cur = array[i];
            while (cur != null){
                int hash = cur.key.hashCode();
                int index = hash % newArray.length;//获取新的下标
                //就是把cur这个节点，以头插方式插入到新的数组
                Node<K,V> curNext = cur.next;
                cur.next = newArray[index];//先绑定到后面
                newArray[index] = cur;//绑定前面
                cur = curNext;
            }
        }
        array = newArray;
    }

    private double loadFactor() {
        return  1.0 * usedSize / array.length;
    }
    public V get(K key){
        int hash = key.hashCode();
        int index = hash % array.length;
        Node<K,V> cur = array[index];
        while (cur != null){
            if (cur.key.equals(key)){
                return cur.val;
            }
            cur = cur.next;
        }
        return null;
    }

    public static void main(String[] args) {
        Person person1 = new Person("123");
        Person person2 = new Person("123");

        HashBuck2<Person,String> hashBuck2 = new HashBuck2<>();
        hashBuck2.put(person1, "bit");

        System.out.println(hashBuck2.get(person2));
    }
    public static void main1(String[] args) {
        Person person1 = new Person("123");
        Person person2 = new Person("123");

        //hashcode():生成一个整数 % length = index

        System.out.println(person1.hashCode());
        System.out.println(person2.hashCode());

        //自定义方法必须重写equals和hashcode方法的
        HashMap<Person, String> map = new HashMap<>();
    }
}
